It is known that salt-inducible promoters exist in plants and cyanobacteria; the latter are rather specialised bacteria which can be used for nitrogen-fixation of soil as natural fertilisation and which taxonomically are quite separate from other bacteria.
Although inducible promoter systems are known in Gram-negative bacteria like E. coli and in the Gram-positive bacterium Bacillus subtilis, while recently in WO 95/31563 (Quest International B.V. (A. Nauta c.s.); see ref. 36) an inducible promoter system was described for lactic acid bacteria or their phages, no literature was found relating to salt-inducible promoters active in microorganisms apart from the above mentioned rather specialised cyanobacteria. Although the expression "salt-initiated induction system" was present in said WO 95/31563 (Quest International B.V. (A. Nauta c.s.); ref. 36), no specific salt-initiated induction system was disclosed.
The present invention provides for the first time a salt-inducible promoter for lactic acid bacteria and its use in the production of polypeptides by lactic acid bacteria.